Investigators on Tuesday raided Lai's apartment in Sanmin District (三民區) of Kaohsiung City (高雄), discovering a computer, eight mobile phones, a stack of white envelopes and work gloves.

CIB Commissioner Lin Te-hua (林德華) said while police were investigating the threatening letters received by Hsiao and Ku, they discovered that the letters shared many similarities with the ones received by Changhua police.

Lin went on to say that the CIB found a total of 27 similar cases across the country, and therefore formed a cross-city taskforce to probe the case.

Judging from the postmarks and saliva left on the envelopes, police on March 5 discovered that Lai, who is wanted for sexual assaults, might be involved in the case, the CIB said.

The bureau said that on the evening of March 11, police followed the suspect back to his apartment, and arrested him with his female friend, surnamed Lin.

Police cited Lai as saying that he admitted sending over 20 letters containing mealworms and ghost money to the victims including Hsiao and Ku, however, he denied sending threatening letters to Din Tai Fung.

The CIB said the case has been transferred to the Changhua District Prosecutors Office for further investigation, noting that it does not rule out the possibility of other copycats sending letters containing worms to the victims.